The present invention relates to a method for continuously wrapping products.
The present invention is advantageously used in the wrapping of foodstuffs, such as chocolates and similar products, to which the following description refers, although without limiting the scope of application of the invention.
In wrapping machines, a succession of products is positioned at regular intervals and fed in an orderly manner along a given path to a pick up station, where the products are gripped by transfer means and fed firstly to a feed station, in which a sheet of wrapping material is associated with each product and, gradually, through a succession of folding stations, designed to form a closed wrapper around each product to be wrapped.
The products are normally fed to the pick up station by an infeed conveyor, whilst the transfer means are normally a rotary conveyor equipped with a plurality of peripheral pick up grippers, which move towards the conveyor in order to pick up the products in succession and transfer them to a first wrapping drum.
The first wrapping drum rotates about a respective axis of rotation and has a plurality of peripheral pick up units, designed to pick up the products and feed them through the feed station and along a folding station in which each sheet is partially wrapped around the relative product to form a wrapper which is substantially folded in a U-shape.
The sets consisting of the products and the relative sheets are then transferred, at a transfer station, to a second wrapping drum, which rotates about a respective axis of rotation parallel with the axis of rotation of the first drum. The second wrapping drum, in turn, has a plurality of peripheral pick up units, each consisting of a pair of jaws set opposite one another, projecting radially away from the drum and arranged symmetrically relative to an axis which is substantially radial relative to the drum. Said jaws are designed to follow a substantially circular path about the axis of rotation of the second drum, in order to feed the sets consisting of the products and sheets through the succession of folding stations.
The folding operations to which each sheet folded into a U-shape must be subjected in order to obtain a closed wrapper encompassing the product envisage a first operation in which each of the two sides of the sheet projecting beyond the corresponding side of the product are folded, thus further folding of the sheet of wrapping material, which assumes the form of a box-shaped, substantially parallelepiped intermediate wrapper inside whose top portion, facing the second drum, the product is housed, whilst the opposite part, the bottom, is open and consists of four side flaps. The side flaps project away from the drum and away from an end surface of the product. Pairs of the side flaps are substantially opposite to and parallel with one another and parallel with the axis of symmetry of the pick up jaws and, specifically, two of the side flaps are parallel with the plane in which the second drum lies and with the circular path.
The subsequent folding operations to which each intermediate wrapper must be subjected in order to obtain a closed wrapper envisage firstly the folding, in succession, of the two opposite flaps which are parallel with the plane in which the second drum lies, so as to define two substantially rectangular wings, in direct contact with the bottom of the product and partially overlapping. The other two flaps assume a substantially triangular or trapezoidal configuration and define a pair of second wings substantially perpendicular to the bottom of the product, which are then folded one on top of the other to completely close the wrapper.
The flaps parallel with the plane in which the second drum lies are normally folded by a pair of folders set opposite one another and having a straight, cyclical alternating motion in a direction substantially perpendicular to the plane in which the second drum lies and the substantially circular path along which the pick up jaws move. The movement of the folders is, therefore, substantially perpendicular to the flaps of the wrapper and the relative folding stage occurs when the productxe2x80x94sheet of wrapping material sets are stopped at the folders.
This folding method has the disadvantage caused by the fact that, in order to increase the speed of production, it has become essential to reduce the time for which the productxe2x80x94sheet of wrapping material sets stop, thus increasing the speed of movement of the folders during their forward and return strokes. This may cause tears in the wrapping materials which form the wrapper, especially those which are not particularly strong, due to the high-level impacts with which the folders make contact with the flaps to be folded. The wrapper may also be moved from its correct position around the product, resulting in a large number of rejects.
The same problem arises in the case of tubular wrappers, wrapped around a product and closed at the sides, in which each of the two ends of the wrapper projecting beyond the ends of the product is folded to define only two side wings, parallel with the plane in which the drum lies.
The aim of the present invention is to provide a method for continuously wrapping products which allows the flaps of a partial wrapper to be folded in such a way that the productxe2x80x94sheet of wrapping material sets do not need to stop and the folding stage is effected gradually, without excessive impacts, and without the disadvantages mentioned above relative to the prior art.
Accordingly, the present invention provides a method for continuously wrapping products, comprising stages for the continuous feed along a given path, an instantaneous tangent of which extends in a first direction which may vary from point to point on the path, of a succession of products to be wrapped, together with respective sheets of wrapping material, at least partially folded around the respective products to define an intermediate wrapper with at least one flap substantially parallel with the plane in which said path lies and projecting in such a way that it is offset from a surface of the product; folding of the flap by at least one folding tool which extends along a respective axis and cooperates with the first flap during the continuous feed of the intermediate wrapper and relative product along an intermediate folding portion of the path. The folding tool moves in a continuous, cyclical fashion along a closed path and moves with a law of motion which derives from the combination of at least two distinct movements, one of which is a movement in a second direction parallel with its own longitudinal axis and transversal to the plane in which the flap lies. The other movement is in the first direction of the path, following the continuous feed of the intermediate wrapper and relative product along the intermediate folding portion, and allowing the flap to be brought into contact with the surface of the product.
The present invention also relates to a device for continuously wrapping products, comprising, along a portion of a wrapping machine equipped with a frame and a wall, a wrapping device having means for feeding, in a continuous fashion and along a given path, an instantaneous tangent of which extends in a first direction which may vary from point to point on the path, a succession of products to be wrapped, together with respective sheets of wrapping material which are at least partially folded around the products to define an intermediate wrapper with at least one flap substantially parallel with the plane in which the path lies and projecting in such a way that it is offset from a surface of the product; a folding device, designed to fold the flap and comprising at least one folding tool which extends along a respective axis and cooperates with the flap during continuous feed of the intermediate wrapper and relative product along an intermediate folding portion of the path. Said folding tool moves in a continuous, cyclical fashion along a closed path and moves with a law of motion which derives from the combination of at least two distinct movements. One is a movement in a second direction parallel with its own longitudinal axis and transversal to the plane in which the flap lies. The other movement is in the first direction of the path, following the continuous feed of the intermediate wrapper and relative product along the intermediate folding portion, and allowing the flap to be brought into contact with the surface of the product.